It has been conventionally known that a laminate including an aluminum foil layer, a thermoplastic resin film layer (inner-side layer) adhering to the inner surface thereof, and an adhesive layer interposed therebetween is used as packaging of a lithium ion secondary cell (cell case packaging).
As the adhesive layer included in the laminate described above, for example, the following adhesive layer has been proposed (ref: for example, the following Patent Document 1). The adhesive layer contains a polyfunctional isocyanate compound and a modified polyolefin resin having a carboxyl group that is obtained by subjecting an ethylenically unsaturated carboxylic acid or an anhydride thereof to graft polymerization with a propylene homopolymer or a copolymer of propylene and ethylene.
The adhesive layer in the following Patent Document 1 has electrolyte resistance that suppresses a reduction over time in the adhesive strength of the aluminum foil layer with the thermoplastic resin film layer caused by contact with an electrolytic solution of the lithium ion secondary cell.